Question: Solve for $x$ and $y$ using substitution. ${x+4y = -6}$ ${x = -6y-8}$
Explanation: Since $x$ has already been solved for, substitute $-6y-8$ for $x$ in the first equation. ${(-6y-8)}{+ 4y = -6}$ Simplify and solve for $y$ $-6y-8 + 4y = -6$ $-2y-8 = -6$ $-2y-8{+8} = -6{+8}$ $-2y = 2$ $\dfrac{-2y}{{-2}} = \dfrac{2}{{-2}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = -6y-8}\thinspace$ to find $x$ ${x = -6}{(-1)}{ - 8}$ $x = 6 - 8$ ${x = -2}$ You can also plug ${y = -1}$ into $\thinspace {x+4y = -6}\thinspace$ and get the same answer for $x$ : ${x + 4}{(-1)}{= -6}$ ${x = -2}$